{"product_id":"national-marker-n350777-square-spring-door-hinge-3-5-in","title":"National Marker N350777 Square Spring Door Hinge 3.5 in","description":"\u003ch3\u003eProduct Description\u003c\/h3\u003e\n\u003cp\u003eThe NATIONAL MARKER N350777 is a 3.5-inch square spring door hinge finished in satin nickel, designed for self-closing door applications in residential, commercial, industrial, and institutional settings. Part of the V520 series, this hinge features adjustable closing tension and adjustable closing speed, giving installers direct control over door return behavior. It is listed for fire-rated openings, making it a code-compliant choice where self-closing hardware is required. Constructed from cold-rolled steel, the N350777 is built for durability in high-cycle environments. Square corners fit standard hinge cutouts without modification.\u003c\/p\u003e\n\u003cp\u003eThis hinge is suited for a wide range of door installations where self-closing function is required by code or building specification. It performs in residential entry and interior doors as well as commercial and institutional corridors, stairwells, and rated assemblies. The adjustable tension and speed settings make it practical for doors of varying weight and swing frequency. Licensed contractors and finish carpenters typically specify this type of hardware when a fire-rated self-closing assembly is required by the authority having jurisdiction.\u003c\/p\u003e\n\u003ch4\u003eKey Features\u003c\/h4\u003e\n\u003cul\u003e\n  \u003cli\u003eAdjustable closing tension allows field calibration to door weight and use frequency\u003c\/li\u003e\n  \u003cli\u003eAdjustable closing speed for controlled door return without slamming\u003c\/li\u003e\n  \u003cli\u003eListed for fire-rated door openings — supports code-compliant self-closing assemblies\u003c\/li\u003e\n  \u003cli\u003eCold-rolled steel construction for strength and wear resistance\u003c\/li\u003e\n  \u003cli\u003eSquare corners fit standard hinge cutouts with no mortise modification\u003c\/li\u003e\n  \u003cli\u003eSatin nickel finish suitable for residential and commercial aesthetic requirements\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch4\u003eCompatibility\u003c\/h4\u003e\n\u003cp\u003eDesigned as an OEM-style replacement and new-installation spring hinge for standard 3.5-inch hinge cutouts on residential and commercial doors requiring self-closing hardware.\u003c\/p\u003e\n\u003ch4\u003eInstallation Notes\u003c\/h4\u003e\n\u003cp\u003eInstallation is typically performed by a licensed finish carpenter, door hardware installer, or general contractor. Before installing or adjusting tension, ensure the door is secured and will not swing freely during work. Use the manufacturer tension adjustment tool or a flat-blade screwdriver as directed to set closing force after mounting. On fire-rated assemblies, verify that all components of the door opening meet the listing requirements of the applicable fire door assembly standard before placing the door in service.\u003c\/p\u003e\n\u003ch4\u003eTechnical Specifications\u003c\/h4\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSeries\u003c\/strong\u003e: V520\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHinge Size\u003c\/strong\u003e: 3.5 inches\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCorner Style\u003c\/strong\u003e: Square\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFinish\u003c\/strong\u003e: Satin Nickel\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMaterial\u003c\/strong\u003e: Cold-Rolled Steel\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFire Rated Listing\u003c\/strong\u003e: Yes\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWeight\u003c\/strong\u003e: 0.779 pounds\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSold As\u003c\/strong\u003e: Each\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch4\u003eStandard Information\u003c\/h4\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBrand\u003c\/strong\u003e: NATIONAL MARKER\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eManufacturer Part Number\u003c\/strong\u003e: N350777\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"NATIONAL MARKER","offers":[{"title":"Default Title","offer_id":51345996644658,"sku":"N350777","price":27.26,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0270\/4519\/9983\/files\/310550650.jpg?v=1782068464","url":"https:\/\/voomisupply.com\/products\/national-marker-n350777-square-spring-door-hinge-3-5-in","provider":"Voomi Supply","version":"1.0","type":"link"}